It is known practice to determine the inclination of an object using motion sensors placed on this object. Inclination should be understood to mean the angle formed by an axis of the object relative to the direction of the field of gravity. These sensors are generally of different kinds such as accelerometers, magnetometers and gyroscopes.
In some applications, the simultaneous use of these sensors of different kinds is not desirable. For example, a gyroscope does not supply sufficient information when the object exhibits a motion of small amplitude. Also, a magnetometer exhibits a great sensitivity to the environment and adds an additional source of noise. Furthermore, the processing of data originating simultaneously from sensors of different kinds is more complex to implement than when there is only one type of sensor.
Methods are thus known for determining the inclination of an object equipped with accelerometers but not equipped with magnetometers and gyroscopes. Such a method is described in the article by K. Parsa et al., “Attitude calibration of an accelerometer array,” Proceedings of the 2002 IEEE International Conference on Robotics & Automation,” p. 129-134, May 2002. This method does, however, require the knowledge of the absolute position of the accelerometers relative to a frame of reference. This can be a drawback in those applications in which the absolute position of the object in the frame of reference is not known.